Drop Node.js 16, upgrade minimal 18 and 20, test 21 #1417

Job	Run time
Test package-lock for unexpected modifications	29s
Install dependencies without using a lockfile	5m 52s
TypeScript compatibility (~5.1)	25s
Node.js (^18.18, ubuntu-latest)	3m 44s
Lint source files	40s
Node.js (^18.18, windows-latest)	10m 11s
Node.js (^18.18, macos-latest)	7m 11s
Node.js (^20.8, ubuntu-latest)	6m 52s
Node.js (^20.8, windows-latest)	8m 8s
Node.js (^20.8, macos-latest)	4m 24s
Node.js (^21, ubuntu-latest)	5m 48s
Node.js (^21, windows-latest)	9m 27s
Node.js (^21, macos-latest)	7m 26s
	1h 10m 37s

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